There is little doubt that flats fishing has a major impact on the Florida Keys economy, but a study released this week gives a clearer picture of just how much revenue it generates.

The fishing conservation group Bonefish Tarpon Trust's study says flats fishing has a direct economic impact of $249 million. That number rises to $427 million after factoring in fishermen's expenses and how their earnings trickle down in the local economy, said Tony Fedler, who conducted the study.

The direct impact of guided flats fishing trips is $62.6 million a year; $107 million after the local trickle-down, the study states.

Flats fishing supports 4,340 full-time jobs in the Keys with an associated annual income of $131 million, the study states. It says flats fishing also generates $31.5 million in federal taxes and $25.9 million in state and local taxes.

Fishing in general in the Keys reportedly has an economic impact of $433 million; $741 million after factoring in fishermen's expenses. It supports 7,536 full-time jobs in the Keys with an associated annual income of $229 million, and generates $54.8 million in federal taxes and $45 million in state and local taxes.

"This study makes a clear point that the economics of the Florida Keys are tied to a healthy marine habitat," Lower Keys flats guide Capt. Will Benson said. "Flats fishing is a major economic component of our community and requires a vibrant and plentiful shallow water resource, which reinforces the need for prudent conservation."

The study also shows fishing is not a secondary or "ancillary" reason why tourists come to the Keys, Benson said. There is a "dedicated, loyal" group of fishermen that "travel to the Keys with the express intention of pursuing game fish in one of the finest fisheries in the world," he said.

Fishermen from all over the world come to the Keys to fish for permit, tarpon and bonefish, he added.

"This is a fishing destination, and not, as tourism officials have said, that fishing in the Keys is a secondary activity," Benson said. "This study reveals that fishing is the foundation of our economy and is very important to the Keys."

The study will most likely wind up being part of the debate over whether to dredge a portion of the Key West shipping channel in order to accommodate larger cruise ships. Fishermen have said dredging will chase away tarpon, as portions of the channel and Key West Harbor are a mecca for tarpon fishing. Thousands are known to migrate through that area in spring and early summer.

"One of the biggest to suffer would be the tarpon," Lower Keys guide Capt. John O'Hearn agreed.

The Florida state record tarpon was caught in Key West by Gus Bell. The 243-pound fish was caught on conventional tackle with 20-pound test line.

O'Hearn also questioned the economic benefit of dredging, as cruise ship passengers spend "significantly less" than fishermen and other tourists who come to the Keys.

The Bonefish Tarpon Trust study states that the average daily expenditure from flats fishing is $288, and $315 for fishing in general. By comparison, a study by National Oceanic and Atmospheric Administration economist Bob Leeworthy in 2009 found that the average cruise ship passenger spent $84 per trip.

Voters will decide Oct. 1 whether the city of Key West will ask the Army Corps of Engineers to conduct a study to determine the impacts of a potential dredging project.